1. Field of the Invention
This invention relates to silane monomers. More particularly, it relates to phenoxyalkoxy-substituted silanes. This invention especially relates to alkyl or alkenyl tris (phenoxyalkoxy) silanes and tetrakisphenoxyalkoxy silanes.
2. Background of the Invention
Organo silanes have found wide use as lubricants, hydraulic fluids, coupling agents in mineral filled polymeric compositions, water repellants, tree retardant additives for polymeric electrical insulation and intermediates in preparing organopolysiloxanes.
U.S. Pat. No. 2,559,342 of Burkhard discloses a family of hydrocarbyl alkoxyethoxy silanes prepared by reacting organochlorosilanes with alkoxyethanols. U.S. Pat. No. 3,814,691 of Csejka et al utilizes organo silanes as a hydraulic fluid base stock. These silanes have the general formula: EQU (R[O--R"].sub.y O).sub.z Si R'.sub.4-z
wherein R is a C.sub.1 -C.sub.10 alkyl or a C.sub.6 -C.sub.10 aryl group, R' is a C.sub.1 -C.sub.4 alkyl group, R" is a C.sub.2 -C.sub.4 alkylene group, y is 1 to 5 and z is 1 to 3. Only nine compounds of the above formula are specifically enumerated and of these only two exemplify a compound where a single alkylene group is present and in both cases the silane is dimethyl. None of the silanes disclosed in U.S. Pat. Nos. 3,048,499 of Jellinek and 2,851,474 of Pines et al. contains an aryl group while all of the organic groups are aryl in the silanes of British Pat. No. 953,421. In U.S. Pat. No. 4,141,851 of Askew et al the most pertinent version of the broad general formula requires two Si-C bonds and two Si-O-C bonds on the single Si atom.
The procedure employed in the Burkhard patent to prepare the organosilanes disclosed therein involves reacting an organochlorosilane with a 2-alkoxyethanol under reflux conditions until HCl evolution is completed. Csejka et al teaches that silanes of this patent are made by reacting an alkyl-halo-silane with polyalkylene glycol monoalkyl or monoaryl ethers in an inert medium.
Copending U.S. patent application Ser. No. 161,932 discloses the addition of organo silanes to polymeric compositions to provide increased resistance to the phenomena known as electrical treeing and water treeing, said compositions being useful as insulation for electrical cables.
Polymeric compositions are well-known and are used extensively as insulation materials for wire and cable. As an insulator, it is important that the composition have various physical and electrical properties, such as resistance to mechanical cut-through, stress crack resistance and dielectric failure. Recent publications have indicated that water tree growth and electrical tree growth in the insulation are particularly important problems since they are associated with, though not necessarily totally responsible for, dielectric failure. The term "tree" has been applied to this type of insulation breakdown since the area of failure is a void space having the appearance of a tree in profile, i.e., the shape of a tree trunk and its upper foliage. Treeing usually is a slowly developing phenomenon and may take years to cause a failure in the insulation.
An important application for an insulation material is in high voltage transmission and distribution cable, especially in direct buried underground service. Two types of trees have been observed in these power cables, to wit, electrical trees and water trees, which are sometimes referred to as electrochemical trees. It is generally believed that electrical trees and generated by corona discharges caushing fusion and breakdown of the polymer, whereas water trees are usually observed in cables buried in wet locations and have a different appearance compared to the electrical trees. Metal ions are usually found in water trees.
U.S. Pat. No. 4,144,202 of Ashcraft et al. relates to inhibiting the electrical breakdown of insulation by water treeing in dielectric materials based on ethylene polymers. As disclosed in the patent, water treeing is inhibited in the ethylene polymer compositions by employing therein organo silane compounds having an epoxy containing radical. German Offenlegungsschrift No. 2,737,430 discloses that certain alkoxysilanes added to polyolefin insulation prevent water-tree formation. Commonly assigned and copending U.S. patent application Ser. No. 161,932, filed June 23, 1980 discloses a number of organosilanes useful as tree retardant additives. Those particularly preferred contain at least one --OC.sub.2 H.sub.4 --O--R group where R is alkyl or aryl. Vinyl-tris (2-phenoxyethoxy) silane is specifically disclosed and exemplified as a useful water tree and electrical tree retardant for polymeric insulation.
It is an object of this invention to provide alkyl or alkenyl tris (phenoxyalkoxy) silanes or tetrakis phenoxyalkoxy silanes.
It is another object of this invention to provide organosilanes useful as water tree and electrical tree retardants.